but I know my decision in advance, I am not going to wait to see if the autobrakes work as advertised
By that convoluted logic I guess you don't use autothrottle in case it doesn't work - you don't use a flight director in case it gives you wrong directions.
But I bet you use the autopilot even though it may not work.
I don't know about other aircraft but the autobrake system in the 737 using RTO position will give you maximum braking. On countless occasions during simulator training we have seen pilots over-riding the RTO (either deliberately or inadvertently) even though it is operating correctly. In nearly all cases the stopping distance using manual braking was significantly greater.
This was especially on an abort due to engine failure where the combination of yaw prevention as reverse thrust is actuated and the slightest delay in correcting the initial asymmetric yaw on the runway when an engine fails, does not affect the RTO braking which is equal on both sets of brakes. Try that with manual braking and it is obvious from the instructor's panel read-out of individual pedal pressures that pilots often have varying brake pedal deflections when coping with an engine failure and abort - especially if a crosswind is present.
Presumably if you do not trust the RTO system you ensure it is selected off before take off? If so, how does that accord with your company SOP's.